In the munitions industry a variety of projectiles have been proposed for permitting delivery of a range of chemical agents for various purposes. These purposes range from marking with a colouring agent, to selective use of designer chemicals for operational purposes such as crowd control and special operations.
There have also been various attempts to produce a frangible projectile for toy guns and for real firearms but none are known to have overcome satisfactorily all the problems that may be encountered. Such problems include:
stable flight, for accuracy and so the projectile with hit nose-first; PA1 sufficient strength to withstand the stress of feeding and firing in a firearm yet frangible enough to break upon impact even upon an unrigid surface; PA1 sufficient sealing so that a filling contained within the projectile does not leak; and PA1 imperviousness to environmental extremes of cold, heat and moisture. PA1 (a) the rear plug is relatively rigid in order to contain the expansive effect of propellant gases; PA1 (b) a recessed compartment in the rear plug contributes to creating a forward centre of gravity for the projectile; and thereby provide a more stable flight; PA1 (c) the barrel rifling is engaged by the projectile in the region of the rear plug only, whereby positive engagement with the barrel rifling imparts spin without bursting the cap portion of the projectile; PA1 (d) the cap itself is isolated from the rifling in the gun barrel by dimensioning the cap fractionally smaller than the gun bore so as to reduce the risk of rupture which could occur from contact with the rifling; PA1 (e) score lines on the forward portion of the cap provide separation of the cap release of the filling on impact; PA1 (f) an indentation region on the nose of the cap facilitates flexing of the score lines for move rapid and efficient bursting of the cap on impact; PA1 (g) complete sealing of the filling compound within the cap is achieved through an integral "O" ring on the plug which mates with an encircling groove within the cap for a snap-on sealing fit; PA1 (h) the score lines extending down the side of the cap do not extend over the plug. PA1 (i) the wall thickness of the cap is selected, in combination with material selection, to resist breakage from lateral impact or handling, while remaining sufficiently frangible on impact so as to be nonlethal. PA1 (ii) is of sufficient viscosity and/or adherence to the wall of the projectile cap to prevent the otherwise destabilizing effect of the compound spinning at a different rate from the cap.